Carbon Intensity of Passenger Transport Modes: A Review of Emission Factors, Their Variability and the Main Drivers

The transport sector is responsible for a significant amount of global carbon emissions, and several policies are being implemented at different levels to reduce its impact. To properly assess the effectiveness of planned measures, analysts often rely on average emission factors for different transport modes. However, average values often hide significant variability that stems from factors along the entire supply chain of transport modes. This review presents a comprehensive overview of research on this topic, comparing emission factors for different passenger transport modes and discussing the main drivers and parameters that affect their variability. The results are useful for researchers and policymakers to properly understand the reliability of carbon intensity indicators when evaluating the impact and effectiveness of sustainable transport policies.